See? This is why I hoped more knowledgeable people would chime in.
Curious though... Can he even push 4x the power into the rears when they are max RMS 25W (compared to the doors max RMS 300W)?
Dangerously more knowledgeable, maybe, because I'm not sure I am interpreting things correctly. Sometimes I look at them backwards.
The amp is rated at 50W max for 4 channels, but 22W per channel at full bandwidth, which matches well with the SO rears.
The Kenwood fronts are rated at 300W peak
, but 30W RMS, so you can overdrive them with the 50W amp, which should be rated RMS.
The issue arises if you have balance and fade set to neutral, the fronts are going to be 4x as loud due to their better sensitivity (90dB vs 84).
Fading to the rear would balance the sound and drastically reduce the power to the fronts, so maybe over-driving isn't a concern.
The key seems to be setting the amp parameters to match the actual speakers, and then not turning the volume up "Too high".
My experience has been that you are more likely to get distortion when the amp is underpowered for the speakers rather than the other way.